淹水培养过程中水稻土地杆菌科微生物群落结构变化特征

采用淹水非种植水稻土微环境模式系统，对水稻土进行1 h和1、5、10、20、30 d淹水培养，利用PCR-DGGE技术检测、多元统计分析淹水培养过程中地杆菌科微生物的群落结构和多样性变化规律及其影响因子。结果表明，淹水培养过程中地杆菌科微生物群落结构发生了明显的演替性变化：由r-对策优势种群演替至k-对策优势种群，且群落结构由不稳定向稳定演变（培养1 h和1 d处理间相似性最低，群落结构变化最大，20 d和30 d处理间相似性最高，群落结构变化最小）；该过程中，地杆菌科微生物物种丰富度指数和Shannon-Weiner指数在1 h处理中均为最小，5 d处理的最大；CCA相关性分析表明，淹水培养过程中Fe（Ⅱ）浓度与群落结构多样性指数呈正相关，证实该类微生物对于异化铁还原能力具有重要作用；测序结果表明，19个优势DGGE条带与来自水稻土中的未培养地杆菌科微生物亲缘关系相近。

Changing Characteristics of Geobacteraceae Community Structure in Paddy Soil During Flooding Incubation

Geobacteraceae is identified as a typical family of dissimilatory iron（ m ） reducer with distribution in anaerobic environment. It plays an important role on the decomposition of organic matter, the suppression of methane production, the bioremediation of heavy metal pollution with valence fluctuation, and the transformation of phosphorus, sulfur and other nutrient elements. In this study, total DNA was extracted from six paddy soil slurries including 1 h, 1 d, 5 d, 10 d, 20 d and 30 d treatments of flooding incubation. The changing characteristics of community diversity and succession of Geobacteraceae were analyzed by using denatured gradient gel electrophoresis （DGGE） based on 16S rRNA gene （rDNA） of Geobacteraceae. The influence factors on characteristics of community diversity and succession of Geobacteraceae in different flooding treatments were analyzed by canonical correspondence analysis （CCA）. It showed that the Geobacteraceae community structure was taken place the successive changes under different flooding time. The r-strategists organisms dominated in the early succession, while the k-strategists organisms gradually replaced them in the late succession. Similarity coefficient indices were the lowest be- tween 1 h and 1 d treatment and the highest between 20 d and 30 d treatment. Richness indices and Shannon-Weiner indices were the high- est in flooding 5 d treatment, and the lowest in flooding 1 h treatment. The result of PCA （principal component analysis） based on digitized DGGE patterns and the sequences showed that the changes of the community structure were stable at the end of flood incubation. The CCA ordination among DGGE profiles and environmental variable factors demonstrated that Fe（ 11 ） concentration strongly correlated with the total variation of the bacterial community. The phylogenetic tree of preponderant DGGE bands could be divided into two groups. The major sequences could get together with the sequences of uncultured Geobacter spp. from paddy soil. The dynamic variation of community structure resulted from different flooding time will provide a theoretical basis to Clarify the characteristics of community structures of iron-reducing bacteria and phylogenetic classification.